DE10261660A1 - White balance method for image projection system, measures absolute power of each beam using sensor and sets beam power for each primary color accordingly - Google Patents

Abstract

A projector produces a color image on a projection surface, or several projectors produce multiple sub-images to form a single color image on the projection surface. A control and evaluation unit (26) controls absolute power measurements of the radiation of each light beam using a sensor (56), and further calculations and settings are carried out accordingly. An Independent claim is included for an apparatus for white balance.

Description

The invention relates to a method and an arrangement for white balance a projection system in which a projector has a colored image on a projection screen generated or in which several projectors generate multiple drawing files, from which a single colored image is put together on the projection surface becomes.

Regardless of the device technology The principle of image generation and image projection is the colored image or each of the partial images from at least three light beams, the are each generated in one of the projectors by additive Color mixing through primary colors generated. One red, one green and a blue beam of light are each an intensity modulator supplied after these intensity modulators become the three bundles of light spatial and / or time-controlled in a projection beam path and / or overlaid on the projection surface.

The additive color composition is suitable for image-imaging projectors, e.g. DLP or LCD, as well as for projectors that work with a writing light beam, a basic physical principle, especially for a laser projector.

With a DLP or LCD projector the generated drawing files are generated in the primary colors and with a Projection optics enlarged to superimposed on the projection surface.

For a projector that works with a writing light bundle works, which is also known under the term "laser projector" one or more collinear light beams using a biaxial one Deflection system distracted so that an image is written as a vector or rasterized line by line. Advantageously, three collinear laser light beams in the three primary colors spatial before the two-axis deflection in a collinear RGB light beam united.

It is known that in projection systems which use the principle of additive color mixing, the power components of the three primary colors have to be adjusted relative to one another for a color-correct image display. As from the DE 43 06 797 C1 can be seen, an achromatic point must be defined for each such image display and for a possible color transformation, which can correspond to the standard illuminant D 65, for example. The module for shifting the color value components contains a network of resistors, which defines a matrix transformation.

By changing the values of the resistors Shifts in the color value components of the three optical channels for the primary colors Red Green and blue corrected by the selective transmission properties of the optical components that are caused by the laser source are subordinate or caused by different laser sources become. This adjustment of the color balance takes place in the path of the video signal from the input to the modulation of the light beam, by for the electronic transmission path a different gain can be selected for each color channel.

In the US 6,259,429 B1 variable resistors are also used for color matching, their arrangement on the matrix transformation in the DE 43 06 767 C1 is due. In the US 6,259,429 the coefficients of the matrix a ₁₁ , a ₂₂ and a _{33 are} constant with 1.

It is also known that performance of laser light sources for each of the primary colors must be set proportionately. For example, in Ch. Deter's publication "Laser Projection Technology" 44th International Scientific colloquium at TU Ilmenau 20, September 1999 Power components a of the RGB laser light source related to the standard illuminant D65 specified, which are theoretically determined to be 100% red (632 nm), 67.9% blue (446 nm) and 95.3% green (532 nm). By regulation the power share of each of the light bundles becomes constant over time the primary valences achieved and thus the power components are set based on "white", or kept stable.

The invention is intended to solve the problem that starting out of the theoretically calculated values for white balance a method and an arrangement can be specified with which for a projector, of the at least three light beams used a white balance can be carried out quickly and with little technical effort can.

In particular, the white balance be made in a projection system, at the multiple projectors generate individual images that form an overall image be put together.

The invention relates to a method for white balance of a projection system that has at least three in a projector light beam different primary colors used that led to modulation in at least one beam path or which are actively generated in one modulator, and in which with overlaid light beams on a projection screen a colored image is generated, with power components α for each of the primary colors based on colorimetric relationships, the focus wavelengths of the Light beam and to a white light point be determined.

The object of the invention is achieved in that, controlled by a control and evaluation electronics unit, absolute power measurements of the radiation of each of the light beams are carried out with a sensor, and to the measurements, as seen in the direction of light propagation, after each of the modulators the light beam is deflected onto the sensor, in this state each of the at least three light beams with their respective nominal power P _{max is} generated and measured one after the other in time and then the primary color is determined by calculations, for the quotient of the nominal power P _max and the power component α the minimum value X _min results then, for each of the other primary colors maximum values of the power output to be adjusted by the control and evaluation electronics unit of the projector P _mod (maximum) = X _min · α calculated, and wherein the measurement, calculation and setting of radiation power for one or more pixels can be carried out for each pixel or a group of pixels for each light beam in the primary colors.

The invention enables an automatic process White balance one or more projectors. The measurement of performance values takes place within the projection system. It is advantageous that the measurement - in the direction of light propagation seen - as far back as possible, that is, the influence as possible many components of the projection system is detected with the measurements.

The method is suitable for use in the well-known projectors. Work this with one The measurements are carried out in the beam path in which the at least three primary colors are guided for each of the primary colors individually and sequentially. Are the light beams in the primary colors in separate beam paths guided, can the measurements in each of the beam paths are also carried out in parallel.

A first embodiment relates to a method for one Projector with a writing, preferably collinear light beam is working. For example, this principle is used in a so-called Laser projector applied.

For the measurements, seen in the direction of light propagation, after a spatial assembly of the light bundles in a common beam path, radiation is deflected onto the sensor, in this state successively each individual one of the at least three light bundles with its respective nominal power P _{max is} generated and measured.

Each of the light beams is after its intensity modulation spatial brought together in the common beam path. The light bundle that is now spatially merged is deflected with a biaxial deflection system that on the projection surface An image is written to measure the radiation's power common beam path of the light bundle or part of it, seen in the direction of light propagation, immediately in front of a biaxial deflecting system deflected onto the sensor.

A second embodiment describes one so-called image-imaging projector, in which for each of the primary colors a real generated source image enlarged on a projection surface becomes. For example, this principle is used in a CRT projector, LCD projector or a DLP projector applied.

Depending on the type of projector, each the beam of light a modulator is supplied to generate monochrome source images or the light beams are actively generated in one modulator at a time. The intensity and spatial modulated light beam are brought together in a common beam path. The spatial merged light beam are then projected onto the projection surface using projection optics, radiation for the power measurement of the common beam path the beam of light or part of it, seen in the direction of light propagation, is deflected onto the sensor in front of the projection optics.

For the modulators that are not active Generate light, each of the light beams is expanded so far that the intermediate images preferably evenly with the respective primary color be illuminated. With active light-generating modulators by means of appropriate control, a uniform brightness generated in the image.

The setting of the performance shares for every the primary colors the projector is either in the electrical transmission path for each of the primary colors or in the optical transmission path for every the primary colors. However, it is also possible Combine electronic and optical means.

The setting of the maximum power output in the electrical transmission path is done in one case by adjusting the gain in each of the electrical channels which of each primary color assigned. As a result, only one of the modulators becomes one Maximum value driven. This maximum value is a common one relative reference point and is usually 100% of the maximum permeability for the Light.

The other modulators are just modulated to below the maximum value. The maximum let through Light output is determined by the maximum possible modulation of the modulator limited. The setting is made on the path of the video signal from Input through to the modulators at a suitable location electronic components for each of the primary colors.

The setting of the maximum power output takes place in the optical transmission path, by setting the maximum possible power that are coupled into each of the modulators. this happens by setting the nominal powers of the light sources for each of the primary colors or through optical components that perform an adjustable power reduction.

It is advantageously provided that the maximum values of the power output for each of the primary colors to generate the white light point are stored in a memory. In this way, values can be obtained about the long-term behavior of the projector.

For full color image display have to at least three light beams are used, in particular in the primary colors red, green and blue are. An expansion of the color space is achieved by using four light beams be in the primary colors Red Green, turquoise and are blue.

The spectral width of each of the light beams should be preferably be less than 10 nm. This is for determining and reproducible Generating the color coordinates is an advantage. The focus wavelengths should yourself during Do not postpone the operation of the projector for optimal and stable white balance make and during the operation of the projector. These properties will met in particular by laser light sources.

Especially for the projectors that use a writing beam of light work, it is imperative that the light beam are collinear. These collinear light beams are advantageous through generates one or more laser light sources. An RGB laser light source generates the at least three light beams in the primary colors or it is a number corresponding to the number of primary colors provided by source lasers. Furthermore, a laser can do more as a primary color deliver and the other primary colors are generated by additional lasers.

Laser light sources are also used for projectors used with the image-imaging Process work, whereby here the light beams to the size of the real ones Source images need to be expanded for example with DLP projectors or LCD projectors.

For an efficiency of the image display, it is advantageous that the light beam or part of the radiation from the light beam at that time only the measurements of the power is diverted into the sensor.

Alternatively, a fraction the radiation of the light beams constantly be coupled out to the sensor. For example, it is sufficient for Measurement from 5% of the radiation from the common beam path of the light beam decouple.

The invention is particularly then an advantage if more than one projector is electrically connected together and be controlled by a control computer. This case lies for example, when six projectors generate partial images, the put together be the area to fill a hemisphere with an image content.

In order to achieve the same color representation for all projectors, the power measurements are carried out for each of the primary colors in each of the projectors. Then the primary color for the one projector is determined by calculations, for whose quotient of the nominal power P _max and the power component α the smallest value X _min results.

Then, for each of the other primary colors of the one projector and for each of the primary colors in the other projectors, maximum working values of the power output P _mod (maximum) = X _min · α are calculated and set by the control and evaluation electronics units of the projectors.

The invention further relates to an arrangement for white balance a projection system operating in a projector at least three light beam used, the radiation of which can be assigned to a primary color, wherein the projector has at least one beam path, in each of which a modulator for intensity modulation the radiation is arranged and subsequently by an overlay the beam of light a colored image is projected onto a projection surface.

The invention is characterized in that that in Seen the direction of light propagation, a device after the modulators provided for decoupling the beam in the beam path of the light beams is and radiation of a decoupled light beam to a sensor Power measurement meets electrically with a control and evaluation electronics unit is coupled to other electronic units for controlling the Radiant power of each of the light beams is connected, the Measurement, calculation and control of the radiation power for one Pixel or several for each pixel or a group of pixels for each light beam in the primary colors be made.

If a projector is used, at which the light beams in the primary colors The measurements are carried out in a common beam path sequentially, individually for each of the primary colors.

With separate beam paths, the Measurements can be made simultaneously.

The sensor is calibrated by Measurement of the power in the rastered light beam after the biaxial Deflection system or in the case of the use of expansion optics after this with a calibrated integrating sphere (power meter) or by measuring the power in the standing light beam after the biaxial Deflection system or in the case of using projection optics after this with a calibrated power meter or by measurement the power in the projection beam path in front of the biaxial deflection system and in front of the sensor with a calibrated integrating sphere, whereby correction factors for the further projection beam path (in the direction of light propagation) are known for a color distortion the biaxial deflection system and the optional transformation optics are determined.

An embodiment of the projectors provides that seen in the direction of light propagation, according to the Modulators in the beam paths are arranged a device for beam combining and after this the device for beam coupling is provided in the beam path of the spatially combined light bundles and radiation from a decoupled light beam strikes the sensor for power measurement.

In a further development of the embodiment the projector uses a light source that is one of the number of primary colors corresponding number of beam paths has in each of which a modulator for intensity modulation of the radiation is arranged. Seen in the direction of light propagation is according to Modulators arranged a device for beam merging. following meet spatially merged light beam on a biaxial deflection system. The facility for Beam coupling is for power measurement in the beam path spatial merged Light beam seen in the direction of light propagation, in front of the biaxial Deflection system arranged. There are biaxial deflection systems for example a combination of a polygon mirror wheel as a line mirror and mirror galvanometers as image mirrors or combinations of tilting mirrors or a two-axis tilting mirror. Suitable as a light source a laser light source is particularly efficient.

An advantageous further development provides that an optical fiber is provided which, seen in the direction of light propagation, has its input after the device for beam combining and its output before the device for coupling out the beam in the beam path of the spatially combined light bundles ( 9 ) Has. The arrangement of an optical fiber between the light source and other components of the projection system enables a very flexible and adaptable projection arrangement.

In a second embodiment a light source is used in the projector, one of the number the primary colors corresponding number of beam paths has, in each of which a modulator for intensity and spatial modulation of the radiation is arranged to generate a monochrome source image. such Modulators generate a source image that is made up of pixels is.

Seen in the direction of light propagation a device for beam combining is arranged after the modulators. Below meet spatially merged light beam on projection optics. The facility is for performance measurement for coupling out the beam in the beam path of the spatially combined light bundles, in Seen light propagation direction, after the device for beam merging or arranged in front of the projection optics.

One measurement is made for each of the Primary colors by controlling all the pixels of the respective channel, or several measurements are made within one channel for each Pixel or for a group of pixels for each of the primary colors.

The light source is after the current one Prior art preferably a temperature radiator. she can but also be a laser light source, the radiation of which depends on the size of the source images was expanded.

In a third embodiment the projector has a number corresponding to the number of primary colors of ray paths, in each of which a modulator for intensity and spatial modulation of the in this actively generated radiation is arranged, for power measurement the device for coupling out the beam in the beam path, in the direction of light propagation seen, is arranged in front of the projection optics. Such projectors use for example TFT or CRT techniques.

The sensor is a photo receiver that Radiant power reproducible in the spectral range used can measure. The use of an integrating sphere is particularly advantageous, in which a photo receiver is installed is.

The setting of the maximum possible Power in each of the beam paths for the primary Color is done by setting the maximum power of each of the source lasers and / or power attenuator in the beam path between the source lasers and the modulators and / or by adjusting the electrical gain in each of the electrical transmission paths. this makes possible a limitation of the maximum let-through power at the modulator, which is arranged in each of the optical channels.

For setting the power via the Source laser will record the characteristics of the power output as a function of the electrical control for each of the at least three Source laser performed.

For setting the power via the Modulators is a recording of the modulator characteristic absorbance as a function of the electrical control for each of the at least three Modulators performed and a determination of the minimum absorbance (corresponds to the maximum Light transmission) for each of the modulators. The white balance is determined by mapping a performance share for each each of the at least three light beams according to the chosen one Weißlichtart made by the Control of each of the modulators according to a working characteristic, which result from the respective modulator characteristic, the respectively measured Power components, the required white light type and the video signal present results.

To set the power by means of power attenuators, the absorbance modulator characteristic curve is recorded as a function of the electrical control for each of the at least three modulators and each of the at least three modulators and one power attenuator (e.g. a λ / 2 plate), each in one beam path are arranged between the light source and one of the modulators, are set to minimal extinction by measuring the power components of each of the three light components with the sensor. The white balance is carried out by assigning a power component for each of the at least three light beams in accordance with the selected white light type by setting each power attenuator (e.g. λ / 2 plates) so that the power components measured by the sensor in each case determine the required white light type result and the control of each of the modulators takes place in accordance with the modulator characteristic and the applied video signal.

The control and evaluation electronics unit the projector is connected to the device for beam coupling and a reflective element of this device for beam coupling is only in the period of power measurements for each of the light beams the common beam path swung in.

In a second case, the facility for beam coupling fixed in the common beam path of the light beams and divides the beam into fractions.

The redirection of light components of the Projection radiation occurs, for example, through an anti-reflective coating Plane parallel plate in the common beam path in front of the biaxial Deflection system or is arranged in front of the projection optics, the one defines proportional part of the radiation of each of the light beams Measurement brings.

The arrangement described above is particularly useful when more than one projector is used for image display. The control and evaluation electronics units each of the projectors are connected to a control computer. Several For example, projectors deliver drawing files that result in a large image together become. For a uniform, holistic composite color image it is particularly important that everyone the projectors have the same "white" and the same colors supplies.

The invention will follow Hand explained by figures. Show it:

1 : Projector with measuring arrangement for white balance in a projection head and with laser diodes as RGB laser light source,

2 : Projector with measuring arrangement for white balance in a projection head with optical fiber connection and with four RGB laser light sources and four modulators,

3 : Projector with measuring arrangement for white balance in a projection head with optical fiber connection with modulators and with λ / 2 plates,

4 : Allocation of the power shares for the primary colors for the examples of 1 to 3 compared,

5 : White balance in a projection system with six projection heads.

6 : DMD projector with a measuring arrangement for white balance with a temperature radiator as a light source

7 : CRT projector with triple measurement arrangement

1 shows the structure of a measuring arrangement for white balance in a projection head 1 , The projection head 1 is via an optical light path of a collinear light beam 9 and a CAN bus with an RGB laser light source 4 connected.

The projection head 1 contains a biaxial deflection system 55 consisting of a polygon mirror wheel 5 as a line mirror and a mirror galvanometer 6 as a picture mirror. The collinear light beam 9 contains the light components red, green and blue spatially combined depending on the degree of modulation.

The laser light source 4 contains the source laser 10 . 11 . 12 one for each light beam in the primary colors red 13 , Green 14 and blue 15 , In the example of the 1 are the source lasers 10 . 11 and 12 Laser diodes, their output by setting the diode current with the help of a laser electronics unit 31 he follows.

The performance of the source laser 10 . 11 . 12 are in video mode according to the video signal VIDEOin via a video electronics unit 30 that with the laser electronics unit 31 connected, between 0% and a maximum value.

A device for beam union 19 summarizes those from the source lasers 10 . 11 and 12 emerging modulated light beams red, green and blue spatially together. The video electronics unit receives for white balance 30 a measurement signal generator 34 , This generates a measurement signal which is an independent, adjustable output of each of the source lasers 10 . 11 and 12 between 0% and 100%.

According to the invention is in the beam path of the collinear light beam 9 between the beam merging device 19 and the polygon mirror wheel 5 a device for beam decoupling 20 provided, which is in a measuring position by means of a mirror 44 the beam of light 9 on a sensor 56 directs. In the example is this sensor 56 an integrating sphere 21 , The mirror is in a working position 44 through the device for beam coupling 20 removed from the beam path; the beam of light 9 meets the polygon mirror wheel 5 (Line mirror). The control of the setting of the device for beam coupling 20 takes place via electrical connection lines 3 through a control and evaluation electronics unit 26 for the white balance, which is connected to the CAN bus. In the control and evaluation electronics unit 26 a sequence control is saved as a computer program. With the CAN bus there is also a scanner electronics unit 28 connected, which via electrical connection lines 3 with a drive and control unit of the polygon mirror wheel 5 and with a drive and control unit of the mirror galvanometer 6 connected is.

Furthermore, the video electronics unit is connected via the CAN bus 30 who have favourited Laser Electronics Unit 31 and a command generator 29 connected.

The integrating sphere 21 has an expansion lens near its opening 22 that act as a light input for the collinear, redirected light beam 9 ' serves, and a diffusely reflective inner wall 23 , At right angles to the beam axis of the integrating sphere 21 incident light is a photo receiver 24 in the inner wall 23 arranged.

Usually inside the integrating sphere 21 an aperture 25 arranged, which prevents incident radiation directly on the photo receiver 24 meets.

The photo receiver 24 delivers signals to the control and evaluation electronics unit 26 for the white balance, which in turn is a manipulated variable for setting each of the power values for each of the source lasers 10 . 11 and 12 supplies. The control and evaluation electronics unit 26 for the white balance also contains a memory for the standard illuminant 27 , in which the percentages for the light components are stored that are intended for the selected standard illuminant. For example, for standard illuminant D65 the values 1 for red, 0.95 for green and 0.67 for blue are saved. By actuating a command transmitter 33 is in the command generator 29 a command to perform the white balance, which is sent via the CAN bus to the corresponding electronic units in the RGB laser light source 4 and in the projection head 1 is transmitted.

• 1. Die Farbart „Weiß" wird für die verwendeten Laserwellenlängen bestimmt, indem die jeweiligen Leistungsanteile für eine Normlichtart für jede der Laserwellenlängen berechnet werden. Dazu wird die gewünschte Normlichtart über den Kommando-Geber 33 eingegeben. Im Speicher 27 der Steuer- und Auswerteelektronikeinheit 26 sind die Daten für wichtige Norm-Lichtarten und die Laserwellenlängen abgelegt. Ein Rechner in der Steuer- und Auswerteelektronikeinheit 26 führt die Berechnung der Leistungsanteile α aus, die aus der Farbmetrik bekannt sind. Für die Normlichtart D6500 ergeben sich für λ = 632 nm α_Rot = 100% λ = 532 nm α_Grün = 97,27% λ = 446 nm α_Blau = 67,41 % Diese Leistungsanteile α werden im Speicher für Parameter der Normlichtart 27 abgelegt.
• 2. Die Kennlinien der Quell-Laser 10, 11, 12 für die roten, grünen und blauen Lichtanteile 13, 14, 15 sind bekannt oder werden jeweils ermittelt. Für den Weißabgleich ist eigentlich nur erforderlich, bei welcher elektrischen Ansteuerung jeder der Quell-Laser minimale und bei welcher elektrischer Ansteuerung jeder der Quell-Laser maximale Leistungsabgabe aufweist. Aus den aufgenommenen Leistungskennlinien für jeden der Quell-Laser werden Meßsignale für 100%ige Aussteuerung gewonnen. (Für die Durchführung der Videoprojektion ist es jedoch erforderlich, die Kennlinien der Quell-Laser in ihrem funktionellen Verlauf zu ermitteln und bei der Ansteuerung der Quell-Laser zu berücksichtigen.)
• 3. Die Leistungsanteile werden für die roten, grünen und blauen Lichtanteile 13, 14, 15 durch Aussteuerung jeder der Quell-Laser 10, 11, 12 durch ein Meßsignal, welches auf den Maximalwert (100%) eingestellt ist, ermittelt. Das Meßsignal entspricht der Vollaussteuerung jedes Quell-Lasers 10, 11, 12 und entspricht der Vollaussteuerung des Videosignals für die jeweilige Primärfarbe. Die Lichtleistungen des roten, grünen und blauen Lichtanteils werden bei 100%iger Aussteuerung der Quell-Laser nacheinander im Projektionskopf mit Hilfe der Ulbrichtkugel 22 gemessen (Die Zahlenwerte sind Beispiele.): Pmax_Rot = 2W Pmax_Grün = 3W Pmax_Blau = 0,8W. Die Ermittlung erfolgt nacheinander für jede einzelne Primärfarbe, wobei die Lichtleistung der jeweils anderen zwei Primärfarben „Null" ist (Quell-Laser auf „Aus").
• 4. Es wird die Primärfarbart ermittelt, die für das System leistungsbegrenzend ist indem Verhältniszahlen x berechnet werden:
  
  Der kleinste Wert ergibt sich bei Blau mit 0,012. Das Minimum bestimmt die begrenzende Primärfarbe. Als Vektor geschrieben:
  
• 5. Aus der die Leistung begrenzenden Primärfarbe (im Beispiel „Blau") werden die Stellgrößen für die Primärfarben „Rot" und „Grün" errechnet:
  
• 6. Aus den Stellgrößen werden die maximalen Werte der modulierbaren Leistungen Pmod für jeden der modulierbaren Quell-Laser 10, 11, und 12 berechnet und dann für jeden der Quell-Laser mittels der Laser-Elektronikeinheit 31 fest eingestellt: Pmod_Rot(Maximal) = Stellgröße_Rot·Pmax_Rot = 1,2 W Pmod_Grün(Maximal) = Stellgröße_Grün·Pmax_Grün = 1,1 W Pmod_Blau(Maximal) = Stellgröße_Blau·Pmax_Blau = 0,8 W
• 7. Es erfolgt die Einstellung der Maximalwerte der modulierbaren Leistungen Pmod (Maximal) der Quell-Laser, so daß bei dem Meßsignal 100% oder bei voll ausgesteuerten Videosignal für jede der Primärfarben die Leistungen im Projektionskopf die Werte bei Rot 60% bei Grün 38% bei Blau 100% der maximal von den Quell-Lasern abgebbaren Leistung Pmax realisiert werden.

The procedure for white balance takes place after entering the command in a command transmitter 33 and its implementation in the command generator 29 in the following steps, automatically by the computer program in the control and evaluation electronics unit 26 controlled:

• 1. The color type "white" is determined for the laser wavelengths used by calculating the respective power components for a standard light type for each of the laser wavelengths. For this purpose, the desired standard light type is selected using the command transmitter 33 entered. In the storage room 27 the control and evaluation electronics unit 26 the data for important standard illuminants and the laser wavelengths are stored. A computer in the control and evaluation electronics unit 26 performs the calculation of the power components α, which are known from colorimetry. For the standard illuminant D6500, the following results for λ = 632 nm α _red = 100% λ = 532 nm α _green = 97.27% λ = 446 nm α _blue = 67.41% These power components α are stored in the memory for parameters of the standard illuminant 27 stored.
• 2. The characteristics of the source laser 10 . 11 . 12 for the red, green and blue light components 13 . 14 . 15 are known or are determined in each case. For the white balance it is actually only necessary for the electrical control with which each of the source lasers has a minimum power output and for which electrical control for each of the source lasers maximum output. Measurement signals for 100% modulation are obtained from the recorded performance characteristics for each of the source lasers. (To carry out the video projection, however, it is necessary to determine the functional curves of the characteristics of the source lasers and to take them into account when controlling the source lasers.)
• 3. The power components are for the red, green and blue light components 13 . 14 . 15 by driving each of the source lasers 10 . 11 . 12 determined by a measurement signal which is set to the maximum value (100%). The measurement signal corresponds to the full modulation of each source laser 10 . 11 . 12 and corresponds to the full modulation of the video signal for the respective primary color. The light outputs of the red, green and blue light components are successively achieved in the projection head with the help of the integrating sphere when the source lasers are controlled 100% 22 measured (the numerical values are examples): Pmax _red = 2W Pmax _green = 3W Pmax _blue = 0.8W. The determination is carried out successively for each individual primary color, the light output of the other two primary colors being “zero” (source laser on “off”).
• 4. The primary color type is determined, which is performance-limiting for the system by calculating ratio numbers x:
  
  The smallest value for blue is 0.012. The minimum determines the limiting primary color. Written as a vector:
  
• 5. The manipulated variables for the primary colors "red" and "green" are calculated from the primary color that limits the output ("blue" in the example):
  
• 6. The manipulated variables become the maximum values of the modulable powers Pmod for each of the modulatable source lasers 10 . 11 , and 12 calculated and then for each of the source lasers by means of the laser electronics unit 31 fixed: P mod _red (maximum) = manipulated variable _red · Pmax _Red = 1,2 W P mod _green (maximum) = manipulated variable _green · Pmax _Green = 1,1 W P mod _blue (maximum) = manipulated variable _Blue · Pmax _Blue = 0.8 W
• 7. The maximum values of the modulatable powers Pmod (maximum) of the source lasers are set, so that with the measurement signal 100% or with a fully modulated video signal, the powers in the projection head for each of the primary colors, the values for red 60% for green 38% with blue 100% of the maximum power Pmax that can be emitted by the source lasers can be realized.

The power setting is therefore due to the source lasers 10 . 11 and 12 for color modulation depending on the signal VIDEOin in the following areas:
with red Pmod _red between 0% and 60%
with green Pmod _green between 0% and 38%
with blue Pmod _blue between 0% and 100%.

With this arrangement and that described The process will balance the performance of the three laser light beams a point within the light path, where with comparative low effort, very practical and above all highly accurate Performance measurement can be made.

The still in the light path, after the device for beam coupling 20 The following assemblies are the polygon mirror wheel 5 , the mirror galvanometer 6 and possibly a transformation optics 41 for angular transformation. The light transmission behavior of these optical assemblies can be assumed to be constant. So it is justified that the transmission behavior of these modules is taken into account by a single calibration of the integrating sphere. For this purpose, we look in the direction of light propagation after the exit of the deflected collinear light beam 9 from the projection head 1 Power measurements were carried out with a calibrated power meter for each of the three laser light beams. The values measured there are compared with those in the Ulbricht sphere 21 measured values are related and are used to calibrate the integrating sphere. This procedure provides sufficiently precise results if it is assumed that the projection surface is "white", ie the projection surface has the same degree of reflection for the primary colors used.

It is also envisaged to include the spectral influence of the projection surface in the calibration of the integrating sphere. This is particularly necessary if the body color of the projection surface deviates from "white". For this calibration, the light reflected from the projection surface of each of the primary colors is measured with the power meter and the values measured there are compared with those in the Ulbricht sphere 21 measured values related. An alternative way of correcting the spectral properties of a projection surface whose body color differs from "white" is to use correction factors for the power shares for each of the primary colors, which take into account the body color of the projection surface.

According to 2 contains the laser light source 4 four source lasers 10 . 11 . 11 ' and 12 for one light beam each in the primary colors red 13 , Green 14 , Turquoise 14 ' and blue 15 which generate the three light components with constant power values. In each case one of these light beams is placed in one of the modulators with a certain fixed power component 16 . 17 . 17 ' and 18 coupled. The modulators are used here for the intensity or power modulation of the light beams. In video mode, the modulators are controlled between 0% and a maximum value according to the video signal present.

The device for beam union 19 summarizes that from the modulators 16 . 17 . 17 ' and 18 emerging modulated light beams red (R), green (G), turquoise (T) and blue (B) spatially together. A coupling optics 7 focuses the spatially combined light bundles in an optical fiber 2 and a decoupling optics 8th forms in the projection head 1 the collinear light beam 9 , To control the laser light source 4 is this with the video electronics unit 30 and the laser electronics unit 31 fitted. The video electronics unit 30 converts incoming video signals VIDEOin into control signals for the four modulators during normal operation 16 . 17 . 17 ' and 18 , The video electronics unit receives for white balance 30 the measurement signal generator 34 which has an independent scalable modulation of each of the modulators 16 . 17 . 17 ' and 18 between 0% and 100%.

According to the invention is in the beam path of the collinear light beam 9 between the decoupling optics 8th and the polygon mirror wheel 5 the device for beam decoupling 20 provided, which in this example from a plate mirror 49 exists, which is constantly in the beam path of the collinear light beam 9 located. The plate mirror 49 constantly directs part of the light beam 9 ' into the integrating sphere 21 into it. The CAN bus is with the scanner electronics unit 28 , the video electronics unit 30 , the laser electronics unit 31 and a control computer 35 connected. Electrical connection lines 3 connect the control and evaluation electronics unit 26 with the photo receiver 24 the integrating sphere 21 as well as the scanner electronics unit 28 with a drive and control unit of the polygon mirror wheel 5 and with a drive and control unit of the mirror galvanometer 6 , The integrating sphere 21 is according to the 1 constructed, the expansion optics being arranged in front of the light entry opening of the integrating sphere.

• 1. Der Farbart „Weiß" wird für die verwendeten Laserwellenlängen bestimmt, indem die jeweiligen Leistungsanteile für eine Normlichtart für jede der Laserwellenlängen berechnet werden. Dazu wird die gewünschte Normlichtart in die Tastatur 32 eingegeben. Im Speicher 27, der sich in diesem Beispiel im Steuerrechner 35 befindet, sind die Daten für wichtige Normlichtarten und die Laserwellenlängen abgelegt. Ein Programm führt die Berechnung der Leistungsanteile α aus. Für die Normlichtart D6500 ergeben sich für λ = 632 nm α_Rot = 100% λ = 532 nm α_Grün = 86% λ = 488 nm α_Türkis = 88% λ = 446 nm α_Blau = 59% Diese Leistungsanteile α werden im Speicher für Parameter der Normlichtart 27 abgelegt.
• 2. Die Kennlinien der Modulatoren 16, 17, 17' und 18 für die roten, grünen, türkisen und blauen Lichtanteile sind bekannt oder werden jeweils ermittelt. Für den Weißabgleich ist eigentlich nur erforderlich, bei welcher elektrischen Ansteuerung der Modulator minimale und bei welcher elektrischer Ansteuerung der Modulator maximale Transmission aufweist. Aus den aufgenommenen Kennlinien für jeden der Modulatoren werden Meßsignale für 100%ige Aussteuerung gewonnen. (Für die Durchführung der Videoprojektion ist es jedoch erforderlich, die Kennlinien der Modulatoren in ihrem funktionellen Verlauf zu ermitteln und bei der Ansteuerung der Modulatoren zu berücksichtigen.)
• 3. Die Leistungsanteile werden für die roten, grünen, türkisen und blauen Lichtanteile durch Aussteuerung jeder der Modulatoren durch ein Meßsignal, welches auf den Maximalwert (100%) eingestellt. Das Meßsignal entspricht der Vollaussteuerung des Modulators und entspricht der Vollaussteuerung des Videosignals für die jeweilige Primärfarbe. Die Lichtleistungen Pmax des roten, grünen, türkisen und blauen Lichtanteils werden bei 100%iger Aussteuerung der Modulatoren nacheinander im Projektionskopf mit Hilfe der Ulbrichtkugel gemessen (Die Zahlenwerte sind Beispiele): Pmax_Rot = 2W Pmax_Grün = 2W Pmax_Türkis = 1W Pmax_Blau = 0,8W Die Ermittlung erfolgt nacheinander für jede einzelne Primärfarbe, wobei die Lichtleistung der jeweils anderen drei Primärfarben „Null" ist (entweder Laser auf „Aus" oder Modulator auf „Null").
• 4. Es wird die Primärfarbart ermittelt, die für das System leistungsbegrenzend ist indem Verhältniswerte berechnet werden:
  
  Der kleinste Wert ergibt sich bei Türkis mit 0,011. Das Minimum bestimmt die begrenzende Primärfarbe. Als Vektor geschrieben
  
• 5. Aus der die Leistung begrenzenden Primärfarbe (im Beispiel „Türkis") werden die Stellgrößen für jede der Primärfarben errechnet:
  
• 6. Aus den Stellgrößen werden die Maximalwerte der Leistungen Pmod (Maximal) berechnet, die nach dem Modulator anliegen können: Pmod_Rot(Maximal)= Stellgröße_Rot·Pmax_Rot = 1,1 W Pmod_Grün(Maximal)= Stellgröße_Grün·Pmax_Grün = 0,95 W Pmod_Türkis(Maximal)= Stellgröße_Türkis·Pmax_Türkis = 1 W Pmod_Blau(Maximal)= Stellgröße_Blau·Pmax_Blau = 0,65 W
• 7. Die Einstellung des Maximalwertes der Leistung Pmod (Maximal), die den jeweiligen Modulator verläßt, erfolgt durch Festlegung eines jeweils maximal möglichen Lichtanteils, so daß bei dem Meßsignal 100% oder bei voll ausgesteuerten Videosignal für eine Primärfarbe die Leistungen im Projektionskopf die Prozentwerte bei Rot 55% bei Grün 43% bei Türkis 100% bei Blau 81% der maximalen Leistung Pmax, die von dem jeweiligen Quell-Laser abgegeben wird, beträgt. Somit liegen die Leistungen Pmod an den jeweiligen Modulatoren zur Farbmodulation abhängig vom anliegenden Signal VIDEOin in folgenden Bereichen: Pmod bei Rot zwischen 0 % und 55% Pmod bei Grün zwischen 0 % und 43% Pmod bei Türkis zwischen 0 % und 100% Pmod bei Blau zwischen 0 % und 81 %.

The procedure for white balance is carried out in the following steps, automatically controlled by a computer program, after input of a command via an input keyboard 32 to a control computer 35 :

• 1. The color type "white" is determined for the laser wavelengths used, by calculating the respective power components for a standard light type for each of the laser wavelengths. For this purpose, the desired standard light type is entered in the keyboard 32 entered. In the storage room 27 , which in this example is in the control computer 35 the data for important standard illuminants and the laser wavelengths are stored. A program carries out the calculation of the power shares α. For the standard illuminant D6500, the following results for λ = 632 nm α _red = 100% λ = 532 nm α _green = 86% λ = 488 nm α _turquoise = 88% λ = 446 nm α _blue = 59% These power components α are stored in the memory for Standard illuminant parameters 27 stored.
• 2. The characteristics of the modulators 16 . 17 . 17 ' and 18 for the red, green, turquoise and blue light components are known or are determined. For white balance, it is actually only necessary for the electrical control with which the modulator has minimal transmission and for which electrical control for which the modulator has maximum transmission. Measurement signals for 100% modulation are obtained from the characteristic curves recorded for each of the modulators. (To carry out the video projection, however, it is necessary to determine the functional characteristics of the characteristics of the modulators and to take them into account when controlling the modulators.)
• 3. The power components for the red, green, turquoise and blue light components are controlled by modulating each of the modulators by means of a measurement signal which is set to the maximum value (100%). The measurement signal corresponds to the full modulation of the modulator and corresponds to the full modulation of the video signal for the respective primary color. The light outputs Pmax of the red, green, turquoise and blue light components are measured one after the other with 100% modulation of the modulators in the projection head using the integrating sphere (the numerical values are examples): Pmax _red = 2W Pmax _green = 2W Pmax _turquoise = 1W Pmax _blue = 0.8W The determination is carried out successively for each individual primary color, the light output of the other three primary colors being "zero" (either laser on "off" or modulator on "zero").
• 4. The primary color type is determined, which is performance-limiting for the system by using ratio values be calculated:
  
  The smallest value for turquoise is 0.011. The minimum determines the limiting primary color. Written as vector
  
• 5. The manipulated variables for each of the primary colors are calculated from the primary color limiting the output (in the example "turquoise"):
  
• 6. The maximum values of the powers Pmod (maximum) that can be applied after the modulator are calculated from the manipulated variables: Pmod _red (maximum) = manipulated variable _red · Pmax _red = 1.1 W Pmod _green (maximal) = manipulated variable _green · Pmax _green = 0.95 W Pmod _turquoise (maximum) = manipulated variable _{turquoise turquoise} · Pmax = 1 W Pmod _blue (maximum) = manipulated variable _{Blue Blue} · Pmax = 0.65 W
• 7. The setting of the maximum value of the power Pmod (maximum), which leaves the respective modulator, is carried out by specifying a maximum possible proportion of light, so that with the measurement signal 100% or with fully modulated video signal for a primary color, the power in the projection head is the percentage value Red 55% for green 43% for turquoise 100% for blue 81% of the maximum power Pmax that is emitted by the respective source laser. The powers Pmod at the respective modulators for color modulation depend on the signal VIDEOin in the following areas: Pmod with red between 0% and 55% Pmod with green between 0% and 43% Pmod with turquoise between 0% and 100% Pmod for blue between 0% and 81%.

The modulator characteristics are adjusted for each of the modulators 16 . 17 . 17 ' and 18 with a limitation of the respective maximum modulation for three of the four modulators below 100%.

The example in 3 corresponds essentially to the projection system, which in 2 is described. Here is an RGB laser light source 4 used, in which the source lasers generate three light components with constant power values. Such a system for three primary colors is for example in the DE 197 13 433.5 C1 described. In the beam path between each of the source lasers 10 . 11 and 12 are the modulators 16 . 17 and 18 arranged.

In contrast to 2 however, is between each of the source lasers 10 . 11 . 12 and each of the modulators 16 . 17 . 18 one beam attenuator each 46 . 47 and 48 arranged, which are used for power adjustment (power reduction). The beam attenuators are, for example, λ / 2 plates 36 . 37 and 38 , By turning the λ / 2 plate accordingly 36 . 37 or 38 The transmitted light output can be about the optical axis, starting from a maximum value for each of the light beams 13 . 14 and 15 can be reduced independently.

Furthermore, here is the sensor 56 a photo receiver 24 , which is in the beam path of the decoupled light beam 9 ' lies.

When determining the parameters for the white balance according to point 3 , the 1 become the λ / 2 plates 36 . 37 and 38 as well as the modulators 16 . 17 and 18 each set to maximum transmission. For setting the white balance according to point 5 , the 1 two of the three λ / 2 plates are rotated in order to achieve the corresponding power reduction for two of the three light components. Other radiation attenuators that can be set, e.g. B. a dielectric mirror that is tilted.

In this example it is an advantage that everybody the modulators in the entire range of its usable characteristic, is controlled up to a maximum of 100%.

Hence, in analogy to 1 , Point 6 .:
Maximum input powers Pein, which are fed into each of the modulators, are calculated from the determined power values Pmax and the manipulated variables. These power values Pein are constant at the input of the respective modulator:
Pein _Red = P mod _red (maximum) = manipulated variable _red · Pmax _Red = 1,2 W
Pein _Green = P mod _green (maximum) = manipulated variable _green · Pmax _Green = 1,1 W
Pein _Blue = P mod _blue (maximum) = manipulated variable _Blue · Pmax _Blue = 0.8 W

The power setting Pein by the λ / 2 plates 36 . 37 and 38 takes place in such a way that the modulators in the measurement signal 100% or in the case of a fully controlled video signal 16 . 17 and 18 fully controlled and for each of the primary colors the powers Pmod (maximum) in the projection head are the percentages
with red 60
with green 38
with blue 100
the maximum power Pmax can be realized.

The power setting is based on that of the source lasers 10 . 11 and 12 output power Pmax depending on the applied signal VIDEOin in the following areas:
for red Pmod _red between 0% and 60
for green Pmod _green between 0% and 38
with blue Pmod _blue between 0% and 100%,
each of the modulators being 100% controllable.

In contrast to 1 is the memory for parameters of the standard illuminant 27 not installed in the control and evaluation electronics unit for white balance. It is located here in the tax calculator 35 , This is for entering commands using an input keyboard 32 connected.

4 shows the assignment of the power shares in comparison for the three examples described above.

In case a), the power components are in accordance with the arrangement 1 shown. Each of the source lasers has a maximum nominal power Pmax. The source lasers are controlled by the control between 0 and a maximum value of the modulable power Pmod.

In case b) the power components are in accordance with the arrangement 2 shown. Each of the four source lasers here has a fixed nominal power Pmax. Due to the reduced control of the modulators in three cases (red, green, blue), the outputs between the modulators have power between 0 and a maximum value of the power Pmod output by the respective modulator. Only the turquoise color modulator is controlled at 100%.

In case c) the power components are in accordance with the arrangement 3 shown. Each of the source lasers has a fixed nominal power Pmax. By setting the three λ / 2 plates, in the example in the beam path of the red and in the beam path of the green light beam to less than 100%, and the λ / 2 plate in the beam path of the blue light beam at 100%, the constantly set powers Pein are applied to the inputs of the modulators. In this example, the modulators themselves are driven up to 100% depending on the VIDEOin signal.

5 shows a projection system, consisting of six RGB laser light sources 4 with associated projection heads 1 , like this one in 3 is described as a single-channel projection system. An arrangement of six coordinated projection heads 1 is useful, for example, for a full dome projection or for image display in a simulator.

The six RGB laser light sources 4 are each electrically via a CAN bus and optically via an optical fiber 2 with one of the projection heads each 1 connected. The video signals VIDEOin are input from a video source 36 , the signals for a respective field of an assigned RGB laser light source 4 and the projection head connected to it 1 supplies.

The six drawing files from the six projection heads 1 are on a projection screen 40 put together into one big picture. In this application, it is of fundamental importance for a high-quality image that the color settings of the six projected images are completely identical.

In order to achieve this goal, each of the projection heads is in principle structured in the way, for example, to 3 is described. The parameters are determined here after entering the standard illuminant and the command for white balance using the input keyboard 32 of the tax calculator 35 , The electronic units are connected via the CAN bus 26 . 28 30 and 31 controlled. With the integrating spheres in each of the six projection heads 1 is being measured.

In this example, the memory is for parameters of the standard illuminant 27 in the tax calculator 29 included and are therefore available to every control and evaluation electronics unit 26 in each of the six projection heads 1 to disposal.

The evaluation of the measurement results for the six projection channels and the three laser light bundles in the primary colors red, green and blue takes place in the control computer 35 following the same procedure as this one too 1 or to 2 has been described. In this example, the minimum power is now 18 measured values calculated further and accordingly the maximum power outputs for each of the three primary colors and in each of the lasers set. For a precise setting, calibration of the measuring arrangement with the integrating spheres by the power meter is also required here 42 required.

In 6 is a DLP projector with a measuring arrangement for white balance with a temperature radiator as a light source 43 shown schematically. Such projectors differ in principle by their optical imaging principle from the projectors described above, which work with a writing light beam. However, the invention can also be used advantageously in image-imaging projectors (for example DLP, CRT or LCD).

The light source 43 emits a white beam of light. This is achieved by dichroic beam splitters (mirrors) 51 and 52 divided into the color components red R, green G and blue B and continued in separate beam paths for each of the light beams. In the example, there are adjustable power attenuators in the direction of light propagation 46 . 47 and 48 arranged by means of the control and evaluation electronics unit 26 are controllable. In the example, these are filters whose transmission can be set, e.g. B. a sliding 20-level gray wedge with the gray levels from 100% to 90% transmission in 0.5% steps or a controllable LCD filter. With the reference symbol 44 all deflecting mirrors are marked. Each of the red, green and blue light beams is applied to one of the modulators 16 . 17 and 18 directed. The modulators here are mirror arrays (DMD). They are used for spatial modulation of expanded light beams. Each mirror element of the array represents a pixel for which intensity or power modulation takes place. The one with the modulators 16 . 17 and 18 Sub-images generated in the primary colors are generated by dichroic mirrors 53 and 54 spatially overlaid. According to the dichroic mirror 54 the superimposed partial images are created using projection optics 50 increased.

According to the invention - seen in the direction of propagation of the light - after the device for beam combining 19 through the dichroic beam splitter here 53 and 54 and the deflecting mirror 44 is formed, the plate mirror 49 as a device for beam coupling 20 in the beam path of the superimposed light beams 9 arranged which is part of the light beam 9 ' into the integrating sphere 21 deflects. The measurement is carried out in an analogous manner to that in 1 The sequence described here, it must be taken into account here that the measurements for each of the pixels belonging together in the respective primary color, a group of these pixels or for all pixels of the matrix are carried out and the performance minimum must be determined via these.

A control electronics unit 45 is about electrical wiring 3 with the light source 43 , the video electronics unit 30 and the modulators 16 . 17 and 18 as well as via the CAN bus with the command generator 29 , the video electronics unit 30 with the measurement signal generator 34 and the control and evaluation electronics unit 26 with the memory for the standard illuminant 27 connected. The control electronics unit 45 is designed for the control of a DMD matrix.

Here, too, the influence of projection optics 50 that are always required in such projectors can be influenced be taken into account in the white balance.

As an alternative to setting the power through the performance attenuators a power setting can also be set here via the modulators themselves respectively.

The example in 7 shows a four-channel CRT projector, in which the three light beams are only brought together on a projection surface. Three images generated by one CRT each are produced by projection optics 50 mapped onto the projection surface and overlaid there as precisely as possible. There are three sensors in such a projector 56 provided that over the facilities for beam coupling 20 each with a redirected beam 9 ' be irradiated. The three independent measurements can be carried out simultaneously, in parallel.

According to the invention - seen in the direction of propagation of the light - after the modulation of the image, here through the cathode ray tube, the plate mirror 49 as a device for beam coupling 20 in the beam of light 9 arranged which is part of the light beam 9 ' into the integrating sphere 21 deflects. The measurement is carried out in an analogous manner to that in 1 Process described, it must be taken into account here that the measurements in each of the three channels red R, green G and blue B are made for each of the pixels in the respective primary color, a group of these pixels or for all pixels of the matrix and via these the The minimum power is determined.

A control electronics unit 45 is about electrical wiring 3 with each of the modulators 16 . 17 and 18 (in this example CRT), the video electronics unit 30 as well as via the CAN bus with the command generator 29 , the video electronics unit 30 with the measurement signal generator 34 and the control and evaluation electronics unit 26 with the memory for the standard illuminant 27 connected. The control electronics unit 45 is designed to control the three CRTs. The control and evaluation electronics unit 26 for white balance here is through the electrical leads 3 with the photo receivers 24 connected.

1

projection head

2

optical fiber

3

electrical cables

4

RGB laser light source

5

line mirror

6

mirror galvanometer

7

coupling optics

8th

output optical system

9

light beam

9 '

deflected light beam

10

Source Laser (Red)

11

Source Laser (Green)

11 '

Source Laser (Turquoise)

12

Source Laser (Blue)

13

red light beam

14

green light beam

14 '

turquoise light beam

15

blue light beam

16

modulator (Red)

17

modulator (Green)

17 '

modulator (Turquoise)

18

modulator (Blue)

19

Facility for beam merging

20

Facility for beam decoupling

21

Integrating sphere

22

expansion optics

23

inner wall

24

photoreceptor

25

cover

26

Tax- and evaluation electronics unit for the white balance

27

Storage for parameters the standard illuminant

28

Scanner electronics unit

29

Command generator

30

Video electronics unit

31

Laser electronics unit

32

input keyboard

33

Command transmitter

34

measuring signal

35

tax calculator

36

video source

37

λ / 2 plate

38

λ / 2 plate

39

λ / 2 plate

40

projection

41

projection optics

42

Power meter

43

light source (Temperature radiator)

44

deflecting

45

Control electronics unit

46

Light attenuator

47

power attenuator

48

power attenuator

49

Splitter mirror

50

projection optics

51

dichroic Beam splitter

52

dichroic Beam splitter

53

dichroic Beam splitter

54

dichroic Beam splitter

55

biaxial working deflection system

56

sensor

R

red

G

green

B

blue

T

turquoise

Claims (25)

Method for white balance of a projection system that has at least three light beams ( 13 . 14 . 15 ) of different primary colors that lead to modulation in at least one beam path or that each in a modulator ( 16 . 17 . 18 ) are actively generated, and in the case of superimposed light beams ( 9 ) on a projection surface ( 40 ) a colored image is generated, the power components α being determined for each of the primary colors on the basis of colorimetric relationships, the focal wavelengths of the light bundles and a white light point, characterized in that a control and evaluation electronics unit ( 26 ) controlled with a sensor ( 56 ) absolute power measurements of the radiation of each of the light beams ( 13 . 14 . 15 ) and to the measurements, viewed in the direction of light propagation, after each modulator ( 16 . 17 . 18 ) Light beam ( 9 ' ) on the sensor ( 56 ) is redirected, in this state each of the at least three light bundles is generated and measured with its respective nominal power P _max and then that primary color is determined by calculations, for which the quotient of the nominal power P _max and the power component α results in the smallest value X _min , then for each of the other primary colors maximum values of the power output P _mod (maximum) = X _min · α calculated by the control and evaluation electronics unit ( 26 ) of the projector can be set, the measurement, calculation and setting of the radiation power for one pixel or several for each pixel or a group of pixels are performed for each light beam in the primary colors. Method according to Claim 1, characterized in that, for the measurements, seen in the direction of light propagation, after a spatial combination of the light bundles in a common beam path, radiation ( 9 ' ) on the sensor ( 56 ) is redirected, in this state each of the at least three light beams with their respective nominal power Pmax is generated and measured one after the other in time. A method according to claim 2, characterized in that each of the light beams ( 13 . 14 . 15 ) are spatially merged in the common beam path after its intensity modulation and continue to be a spatially merged light beam ( 9 ) with a biaxial deflection system ( 55 ) is distracted so that on the projection surface ( 40 ) an image is written, with radiation of the common beam path of the light beams (for power measurement) 9 ) or a part of it, seen in the direction of light propagation, directly in front of a biaxial deflection system ( 55 ) on the sensor ( 56 ) is redirected. A method according to claim 2, characterized in that each of the light beams ( 13 . 14 . 15 ) to generate monochrome source images using a modulator ( 16 . 17 . 18 ) is supplied or the light beams ( 13 . 13 . 15 ) in one modulator ( 16 . 17 . 18 ) are actively generated and then the intensely and spatially modulated light bundles are brought together in a common beam path and furthermore the spatially combined light bundles ( 9 ) with projection optics ( 50 ) on the projection surface ( 40 ) are projected, whereby radiation of the common beam path of the light bundles ( 9 ) or a part of it, seen in the direction of light propagation, in front of the projection optics ( 50 ) on the sensor ( 56 ) is redirected. A method according to claim 1, characterized in that the Setting the power shares in the electrical transmission path for every the primary colors and / or in the optical transmission path for every the primary colors he follows. A method according to claim 5, characterized in that the Setting the maximum power output in the electrical transmission path is done by adjusting the gain in each of the electrical channels which is assigned to the respective primary color. A method according to claim 5, characterized in that the Setting the maximum power output in the optical transmission path done by setting the maximum possible power to each of the optical channels which is assigned to the respective primary color. A method according to claim 1, characterized in that the maximum values of the power output (Pmod (maximum) for each of the primary colors to generate the white light point get saved. A method according to claim 1, characterized in that three light beam used in the primary colors red, green and blue are or that four light beam used in the primary colors red, green, turquoise and Are blue. A method according to claim 1, characterized in that the spectral width of each of the light beams is less than 10 nm. A method according to claim 1, characterized in that the light beams are collinear and in particular by an RGB laser light source ( 4 ) that generate at least three light beams in the primary colors or that have a number of source lasers corresponding to the number of primary colors ( 10 . 11 . 12 ) Has. A method according to claim 1, characterized in that the radiation of the light beams or part of this radiation only at the time of the measurements of the powers in the sensor ( 56 ) is redirected. Method according to Claim 1, characterized in that a fraction of the radiation from the light beams is continuously applied to the sensor ( 56 ) is coupled out. Method according to one or more of the preceding claims from 1 to 13, characterized in that more than one projector is electrically connected together and by a control computer ( 35 ) can be controlled, the power measurements for each of the primary colors being carried out in each of the projectors and then the primary color for the one projector being determined by calculations, for whose quotient of nominal power P _max and power component α the smallest value X _min results, then for each of the other primary colors of the one projector and for each of the primary colors in the other projectors maximum work values of the power output P _mod (maximum) = X _min · α are calculated and set by the control and evaluation electronics units of the projectors. Arrangement for white balance of a projection system, which uses at least three light beams in a projector, the radiation of which can each be assigned to a primary color, the projector having three beam paths, in each of which a modulator ( 16 . 17 . 18 ) is arranged for intensity modulation of the radiation and subsequently by superimposing the light beams ( 9 ) a colored image on a projection surface ( 40 ) is projected, characterized in that viewed in the direction of light propagation, after the modulators ( 16 . 17 . 18 ) a device for beam coupling ( 20 ) is provided in the beam path of the light beams and radiation from a coupled light beam onto a sensor ( 56 ) for power measurement, which is electrical with a control and evaluation electronics unit ( 26 ) is coupled with other electronic units ( 32 . 33 . 35 . 30 . 31 . 45 ) is connected to the control of the radiation power of each of the light bundles, the measurement, calculation and control of the radiation power for one pixel or several of them being carried out for each pixel or a group of pixels for each light bundle in the primary colors. Arrangement according to claim 15, characterized in that viewed in the direction of light propagation, after the modulators ( 16 . 17 . 18 ) a device for beam combining in the beam paths ( 19 ) is arranged and after this the device for beam coupling ( 20 ) in the beam path of the spatially combined light bundles ( 9 ) is provided and radiation from a decoupled light beam ( 9 ' ) on the sensor ( 56 ) to measure performance. Arrangement according to claim 16, characterized in that the projector has a light source which has a number of beam paths corresponding to the number of primary colors (R, G, B, T), in each of which a modulator ( 16 . 17 . 18 ) is arranged for intensity modulation of the radiation, viewed in the direction of light propagation after the modulators ( 16 . 17 . 18 ) a device for beam merging ( 19 ) is arranged and subsequently spatially merged light beams onto a biaxial deflection system ( 55 ), the device for beam coupling ( 20 ) for power measurement in the beam path of the spatially merged light bundles, seen in the direction of light propagation, in front of the biaxial deflection system ( 55 ) is arranged. Arrangement according to claim 16 or 17, characterized in that an optical fiber ( 2 ), which is seen in the direction of light propagation, its entrance after the device for beam combining ( 19 ) and its exit in front of the beam coupling device ( 20 ) in the beam path of the spatially combined light bundles ( 9 ) Has. Arrangement according to claim 15 or 16, characterized in that the projector is a light source ( 43 ) and has a number of beam paths corresponding to the number of primary colors (R, G, B), in each of which a modulator ( 16 . 17 . 18 ) is arranged for intensity and spatial modulation of the radiation to produce a monochrome source image, the device for beam coupling () for power measurement ( 20 ) in the beam path of the light beams ( 9 ), seen in the direction of light propagation, in front of the projection optics ( 50 ) is arranged. Arrangement according to claim 15 or 16, characterized in that the projector has a number of beam paths corresponding to the number of primary colors (R, G, B), in each of which a modulator ( 16 . 17 . 18 ) is arranged for intensity and spatial modulation of the radiation actively generated in it, the device for beam coupling () for power measurement 20 ) in the beam path, seen in the direction of light propagation, in front of the projection optics ( 50 ) is arranged, Arrangement according to claim 15, characterized in that the sensor ( 56 ) a photo receiver ( 24 ) or an integrating sphere ( 21 ) with built-in photo receiver ( 24 ) is. Arrangement according to claim 15, characterized in that the setting of the maximum possible power in each of the beam paths for the primary colors by setting the maximum power of a light source ( 10 . 11 . 12 ) and / or through reduced performance ( 46 . 47 . 48 ) in the beam path between the light source ( 10 . 11 . 12 ) and the modulators ( 16 . 17 . 18 ) and / or by adjusting the electrical gain in each of the electrical transmission paths. Arrangement according to claim 15, characterized in that the control and evaluation electronics unit ( 26 ) with the device for beam coupling ( 20 ) is connected and a mirror ( 44 ) this device for beam coupling only in the period of the power measurements for each of the light beams ( 9 ' ) in the common beam path of the light beams ( 9 ) can be swiveled in. Arrangement according to claim 15, characterized in that the device for beam coupling ( 20 ) as a divider mirror ( 49 ) firmly in the common beam path ( 9 ) is arranged and divides the beam into fractions. Arrangement according to one or more of the preceding claims from 15 to 24, characterized in that more than one projector is used for image display and the control and evaluation electronics units ( 26 ) each of the projectors with a control computer ( 35 ) are connected.